The Berserker (バーサーカー, Bāsākā?) Class Card of the Fifth Ainsworth Holy Grail War was granted to Beatrice Flowerchild in Fate/kaleid liner PRISMA☆ILLYA. It was later one of eight Class Cards transported to Illya's world.
When manifested, Heracles has the same appearance as he normally does in the Berserker class. As he continues to battle, his elbow protrusions begin to grow into a number of spikes and similar protrusions begin to grow on his body.
The Berserker Class Card is the last of the standard Class Cards to be found, located inside a building with a barrier much smaller than that of previous Class Cards. Miyu Edelfelt tries to fight it alone, but becomes completely overwhelmed by Berserker after she manages to kill him once with Gae Bolg. Installing the Saber Class Card is able to allow her to fight him back and strike with Excalibur, but it proves ineffective in fully killing him. Illya arrives before Berserker can finish Miyu off, and while Rin and Luvia briefly hold him down, Miyu and Illya use Kaleid Install with the Saber Class Card to finish him off. It's card was rarely used due to how it's Include, Nine Lives , was too heavy to be used profeciently and the overall lack of information surrounding it.
It was briefly used by Illya as a Include against Gilgamesh but he counters by also summoning the Nine Lives in its orignal form.
It was then fully utilized as an Install by Illya in her battle againt Beatrice Flowerchild against her Berserker Card. Despite orignally fighting on equal grounds, Beatrice was proven to be still surperior with her Berserker. Illya manages to counterattack by overwriting the Installed Berserker Card with the Rider Card which resulted in a Installed state where the Heroic Spirit of Rider inherited the Berserker Class.
While Heracles' Axe-Sword is present in the Include function of the Class Card, the manifested Heracles does not posses it, instead only using his fists to fight and God Hand to revive. God Hand is ranked down and only blocks against attacks C-rank and below. It still is able to resurrect him and nullify attacks that have previously harmed him.
Including the Class Card grants Nine Lives in the form of Berserker's large axe-sword. Normally a style of martial arts that was adapted from his bow and arrow used to slay the hydra, it can be used with any weapon. The martial art of the Noble Phantasm has been lost, so only the sword is deployed.
Installing it grants Heracles' ability at the cost of removing the user's reason due to Mad Enhancement. Normally an "excellent Heroic Spirit in every aspect", the Installation leaves on a "monster who destroys the enemy in front of one's eyes and without reflecting on one's body." While the user gains God Hand, the Installation deteriorates it in various ways and leaves it with a fewer stock of lives than normal. It gives the user Heracles' clothing, adding a bit of cloth to the chest if done by a female, and gives the axe-sword as a weapon.
It is shown that one can overwrite the Installed Heroic Spirit of Berserker with another Heroic Spirit Class Card, granting the later the Berserker Class.